Patent Literature (PTL) 1 discloses, allocating the storage apparatuses in the pool to virtual volumes in accordance with access from the host to the virtual volumes, powering on the storage apparatuses allocated to the virtual volumes, and powering off the storage apparatuses in preparation status not allocated to the virtual volumes to reduce power consumption of the storage apparatuses allocated to the pool, in a storage system including a structure of providing virtual volumes supplied from a pool configured of a set of storage apparatuses and to which storage apparatuses can be added afterwards to a higher-level devices.